There has been commercialized a multiple pane. In the multiple pane, a pair of glass panels are arranged facing each other, and a plurality of spacers are interposed between the pair of glass panels, and the pair of glass panels are bonded with a hermetically bonding member at peripheries thereof, and thus an inside space is defined by the pair of glass panels and the hermetically bonding. The air in the inside space is exhausted to reduce the pressure of the inside space.
It is expected that the multiple pane in which the pressure of the inside space is reduced shows great thermally insulating effects, dew prevention effects, and sound insulating effects, as a result of presence of a vacuum layer whose pressure is lower than the atmospheric pressure between the pair of glass panels, relative to a multiple pane constituted by two glass plate simply bonded to each other. Therefore, such multiple pane attracts great attentions as one of eco-glass in current situations in which the importance of energy strategy rises.
The multiple pane including the inside space with the reduced pressure is produced as follows: the peripheries of the pair of glass panels are hermetically bonded by applying the hermetically bonding seal of low-melting glass frit therebetween and heating them to hermetically bond the peripheries to form a space while a plurality of spacers of metal or ceramics are interposed to keep the predetermined distance between the glass panels, and thereafter air is evacuated from the space via an evacuation pipe of glass or metal. The multiple pane is produced through this production process, and thus the finished product of the multiple pane including the inside space with the reduced pressure includes the evacuation pipe whose tip is closed. Hence, in the multiple pane constituted by transparent glass panels, the evacuation pipe may cause problems that appearance becomes poor and the inside space cannot be kept in the reduced pressure state when the evacuation pipe is broken. In view of this, with regard to the multiple pane used as a window pane, for example, the multiple pane is used so that the evacuation pipe is positioned at the upper-right corner of the indoor side. In other words, the use of the multiple pane is limited so as to prevent visually and physically interference of the evacuation pipe.
In a technique which has been proposed as the conventional production method of multiple pane with the reduced pressure, an evacuation pipe is embedded into one of glass panels until a center in a thickness direction, and the evacuation pipe is sealed with shield for preventing a junction of the glass panel and the evacuation pipe from suffering from heat generated in sealing the evacuation pipe. According to this technique, the evacuation pipe remaining in the finished product is shortened (see patent literature 1 [JP 10-2161 A]). In another technique, an evacuation pipe and a vicinity of a part, on which the evacuation pipe is situated, of a rear surface of a glass panel are covered with a cover member of resin so as to form a gap between the cover member and a sealed tip of the evacuation pipe. According to this technique, breakage of the evacuation pipe caused by impacts from outside can be prevented (see patent literature 2 [JP 11-311069 A]).
According to the conventional production method of multiple pane described above, in the finished product, the evacuation pipe becomes short, and thus the multiple pane can be easy in handling. External force directly acting on the evacuation pipe can be suppressed, and thus it is possible to prevent an unwanted situation where the reduced pressure state cannot be maintained due to breakage of the evacuation pipe. Therefore, the conventional production method can give advantageous effects to an extent.
However, for example, in the techniques disclosed in patent literature 1, it is necessary to form a recess in the glass panel and fix the evacuation pipe inside the recess in order to reduce an amount of part of the evacuation pipe protruding from the surface of the glass panel. Further, the shield disposed so that the temperature of the junction of the evacuation pipe and the glass plate becomes high at the time of sealing the evacuation pipe is necessary. Thus, the production process of multiple pane becomes more complex. Additionally, according to the technique disclosed in patent literature 2, it is necessary to add the cover member, and this causes an increase in the number of parts. Further, it is necessary to add a step of attaching the cover member to the rear surface, and this causes an increase in the number of steps. When the production process becomes more complex and the numbers of parts and steps increase, the production cost of the multiple pane tends to increase. Further, in the multiple panes formed by use of the above conventional techniques, the evacuation pipe still remains in the finished product. Hence, such a protrusion from the rear surface of the multiple pane is present and therefore there is a problem of appearance, it is very difficult to perfectly eliminate a risk in which the space formed by the pair of glass panels cannot be kept in the reduced pressure state when the evacuation pipe is broken.